The "Breast Cancer Prevention" program is designed as an integrated multidisciplinary cancer control project. It focuses on biological, genetic, psychologic and pharmacologic studies in women at enhanced risk for breast cancer. The original 2-arm pilot study was redesigned. The current study is designed as a 3-arm randomized controlled double-blind pilot trial established to meet the following objectives: (1) to evaluate the proposed biomarker using a radiometric assay in terms of (a) within subject and between subject variability and (b) levels in 5 risk groups; (2) to validate the biomarker by either serum or urine spot test; (3) to assess consent to enter and compliance in the trial; (4) to evaluate toxicity of the interventions; (5) to observe the efficacy of the intervention in terms of favorable perturbation of the biomarker. The 3 arms are: (1) Omega-3 Fatty Acids & Placebo for Thyroxine (2) Thyroxine & Placebo for Omega-3 Fatty Acids (3) Placebo for Thyroxine & Placebo for Omega-3 Fatty Acids Prior to the start of the interventions, the subjects will have an initial clinic visit at which we will obtain baseline information, and the first radiometric biomarker analyis will be carried out. Follow-up clinic visits are scheduled at 4 months, 8 months, and 12 months for the primary purpose of monitoring compliance and toxicity. At 4-6 months after start of interventions, the second radiometric biomarker analysis will be completed. Each subject will act as her own control in evaluating the efficacy of the agents in perturbing the biomarker. The long term objective of this trial is the reduction of human breast cancer rates.